| Popis: |
The Doppler-shift attenuation method was used to obtain the following mean lifetimes (in psec) for the indicated nuclear levels: $^{10}\mathrm{C}$(3.36), $\ensuremath{\tau}=0.155\ifmmode\pm\else\textpm\fi{}0.025$; $^{10}\mathrm{B}$(3.59), $\ensuremath{\tau}=0.150\ifmmode\pm\else\textpm\fi{}0.015$; $^{10}\mathrm{Be}$(3.37), $\ensuremath{\tau}=0.189\ifmmode\pm\else\textpm\fi{}0.020$; $^{10}\mathrm{B}$(2.15), $\ensuremath{\tau}={{2.7}_{\ensuremath{-}0.4}}^{+0.5}$. A limit of $\ensuremath{\tau}l30$ fsec is obtained for $^{10}\mathrm{B}$(1.74), which is a factor of 8 greater than, and therefore consistent with, the lifetime computed from the analog $\ensuremath{\beta}$ decay of $^{10}\mathrm{C}$. Transition strengths obtained from the $^{10}\mathrm{B}$(2.15) and $^{10}\mathrm{B}$(3.59) lifetimes are in good agreement with the effective-interaction calculations of Cohen and Kurath, as modified by Warburton et al. The $^{10}\mathrm{C}$(3.36) and $^{10}\mathrm{Be}$(3.37) states decay by analog $E2$ transitions: ${2}^{+}$, $T=1\ensuremath{\rightarrow}{0}^{+}$, $T=1$, with ${T}_{z}=\ifmmode\pm\else\textpm\fi{}1$, whose strengths are well described by calculations of Kurath's for an effective charge ${\ensuremath{\epsilon}}_{n}={\ensuremath{\epsilon}}_{p}=0.5$. An upper limit was obtained for the corresponding transition 5.17 \ensuremath{\rightarrow} 1.74 in $^{10}\mathrm{B}({T}_{z}=0)$ which is consistent (factor of 4 greater) with the analog strengths observed in the ${T}_{z}=\ifmmode\pm\else\textpm\fi{}1$ nuclei. |
